This application claims benefit of priority to Japanese Patent Application No. JP10-255516 filed Sep. 9, 1998, the entire disclosure of which is incorporated by reference herein.
1. Field of the Invention
The present invention relates to an elevator having a cage suspended by cables putting around car sheaves.
2. Description of the Background
FIG. 1 is a front view of one example of a traction type elevator and FIG. 2 is a perspective view of an elevator cage shown in FIG. 1.
In FIG. 1 and FIG. 2, opposite ends of a cable 82 are secured to the upper part of a shaft 83. The cable 82 is placed around a traction sheave 85 driven by a hoisting machine 84 having a motor (not shown). A cage 80 for accommodating passengers and a counterweight 86 for balancing the cage 80 are suspended by the cable 82 through a weight sheave 87 of the counterweight 86 and car sheaves 81 of the cage 80.
In this type of elevator, the cable 82 and the traction sheave 85 are located within the space between the cage 80 and a shaft wall 88. Therefore, if the hoisting machine 84 driving the traction sheave 85 is located within the space between the cage 80 and the shaft wall 88, the cage 80 can move up and down without expanding the size of the shaft 83.
The weight of the counterweight 86 is designed to be approximately half of the maximum permissible load of the cage 80. That is, if the maximum permissible load of the cage 80 is 1,000 lbs, the weight of the counterweight 86 is 500 lbs. When passengers weighing half of the maximum permissible load board the cage 80, the cage 80 and the counterweight 86 are nearly balanced.
As shown in FIG. 3, the cage 80 is composed of a cab 106 and a cage frame around the cab 106. The cage frame is composed of a crosshead 104, a pair of uprights 105, a plank 109 is configured to be fitted between a pair of guide rails 103. The cab 106 has a car platform 111 and the car platform is secured to the plank 109 through anti-vibration materials (not shown) such as rubber. A support base 121 having a pair of axles 123 is attached to a lower side of the plank 109. The axles 123 are respectively arranged in parallel so as to be perpendicular to the cable 82 positioned between the car sheaves 81 and rotatably support the car sheaves 81. The cable 82 is driven by traction between the cable 82 and the traction sheave 85, and the cage 80 is moved up and down by the cable 82 along the guide rails 103.
However, in the above mentioned elevator, since the car sheaves 81 installed near the car platform 111 experience high speed rotation in contact with the cable 82, vibration and noise caused by the contact can be easily transferred to the cage 80.
Further, vibration caused by a change in tension of the cable 82 around a hoisting machine can be transferred to the cage 80 via the car sheaves 81. This tension change sometimes occurs at the time the torque of the motor of the hoisting machine 84 changes.
Accordingly, one object of the invention is to provide an elevator suspended by a cable through car sheaves, wherein vibration transferred from the cable can be attenuated to improve comfort of a ride in the cage.
This and other objects are achieved according to the present invention by providing a new and improved elevator including a cage for accommodating passengers configured to move up and down in a shaft along a guide rail, a support base attached to a lower portion of the cage, a plurality of car sheaves rotatably secured to the support base through respective axles, a cable placed around the car sheaves and configured to suspend the cage, and at least one damper coupled to the cage and configured to attenuate vibration transferred from the cable to the cage.